1. Field of the Invention
The present invention relates to a method of fabricating a one-way transparent optical system and, more particularly, to a method of fabricating a one-way transparent optical system by which external light is effectively intercepted and internal light passes nearly without loss.
2. Description of the Related Art
When using an emissive type display device such as an organic electroluminescent (EL), external light is reflected on the surface of the display device so that glare occurs and contrast decreases due to the external light reflected by a metallic electrode. To prevent these problems, in the prior art, an antireflective coating, a polarizer, and a ¼ waveplate, as shown in FIG. 1, have been used. That is, reflection of external light 20 on the surface of the display device is minimized using an antireflective coating, thereby preventing glare. A polarizer 12 and a ¼ waveplate 11 are formed on the surface of the display device and suppress re-emission of external light incident into the display device, thereby preventing a decrease in contrast. That is, as shown in FIG. 1, the external light 20 that has passed through the polarizer 12 has only linear polarization components. The external light 20 having only linear polarization components is changed into circular polarization by the ¼ polarization plate 11, and thus does not pass through the polarizer 12 during reflection. Thus, re-emission of external light incident into the display device is suppressed.
However, in the prior art, due to the ¼ waveplate 11 and the polarizer 12, emission of internal light as well as external light is limited so that only about 50% more internal light can be emitted from the inside of the display device. Thus, in a conventional structure for preventing glare and a decrease in contrast, optical efficiency and brightness of the display device are decreased.
FIG. 2 shows an organic electroluminescent (EL) element having a glare-preventing structure using a light-absorbing material, instead of a polarizer. Referring to FIG. 2, in the organic EL element in which a first electrode 22, a hole injecting layer 23, a hole transporting layer (HTL) 24, an organic light-emitting layer 25, an electron transporting layer 26, an electron injecting layer 28, and a second electrode 29 are consecutively stacked on a transparent substrate 21, the electron transporting layer 26 is doped with a light-absorbing material. However, in this structure, since internal light generated in the organic light-emitting layer 25 is also absorbed by the light-absorbing material, only the effects of reducing manufacturing costs are achieved, unlike a structure using a polarizer.
FIG. 3 illustrates a structure of a display device for preventing glare using extinguishment interference. Referring to FIG. 3, the display device has a structure in which a light-emitting layer 32, a second electrode 33, a top protective layer 34 and an antireflective coating layer 35 are consecutively stacked on a first electrode 31. In addition, the first electrode 31 includes a semi-transmission layer 31a, a transmission layer 31b, and a total reflection layer 31c. In this structure, a part L1 of external light is not reflected by the antireflective coating layer 35 but absorbed. Part L2 of light L2 and L3 that have passed through the antireflective coating layer 35 is reflected by the semi-transmission layer 31a and the other part L3 thereof is reflected by the total reflection layer 31c. In this case, light L2 reflected by the semi-transmission layer 31a and light L3 reflected by the total reflection layer 31c interfere with each other and are extinguished. However, even in this structure, since part of internal light generated in the light-emitting layer 32 is reflected by the semi-transmission layer 31a and the total reflection layer 31c and extinguished, internal light also decreases.